Molten urea dyeing process



2,930,670 MOLTEN UREA DYEING PROCESS Samuel Nelson Bradshaw, oyentry,and Harry B. Mann, Braintree, England, a'ssignors to Courtauids Limited;London, England, a British company No Drawing. Application July 24, 1956Serial No. 607,252 Claims priority, application Great Britain July29,1955 Claims. (Cl. 8-85) This invention relates to the dyeing oftextile materials.

In the normal dyeing procedure textiles are treated with an aqueoussolution or dispersion of a dyestuff at a temperature depending on thenature of the material being dyed and the materials are left in thedyebath for a considerable period and are then rinsed and dried. Thedyebath may also contain one or more dyeing assistants, for examplecommon salt or Glaubers salt or other compounds which assist thematerial in taking up the dye.

and give a uniform penetration of the material by the dye. In the normaldyeing process therefore, water is the usual medium in which the dye istransferred'to the textile materials but in the specification ofco-pending application U.S. Serial No. 428,375, filed May 7, 1954, andits continuation-impart Serial No. 668,043, filed June 26, 1957, thereis described a method of dyeing in which molten urea replaces water asthe dyestuff transfer medium. In this method textile materials aretreated with a dyestutf in the presence of urea and are maintained at atemperature between the melting point of urea and 160 C. Thus textilematerials may be impregnated with an aqueous solution or dispersion ofthe dyestuif and the urea, the impregnated material is dried and thenbaked at a temperature above the melting point of the urea.

In any dyeing process, it is generally desirable for economic or otherreasons to carry out the process at the lowest practicable temperatureand accordingly, the ob ject of the present invention is to modify theprocess of (1.8. Serial No. 428,375 and its continuation-in-part SerialNo. 668,043, filed June 26, 1957, to enable lower temperatures to beused.

According to the present invention textile materials are treated with adyestuif in the presence of urea and one or more other substancessoluble in urea and capable of lowering the melting point of the ureaand are maintained at a temperature between the melting point of themixture and 160 C.

The amount by which the melting point is lowered will depend on thenature and quantity of the-substance or substances added. Any suitablesubstance (hereinafter referred to as a melting point depressant ordepressant) soluble in molten urea and capable of lowering its meltingpoint may be used. These depressants may be used in amounts up to of theweight of the urea, or up to their maximum solubility in urea if this isless than /s. The following table gives examples of suitable substancestogether with their maximum solubility in urea 2,930,670 Eaten-ted ,Mar.29-, 1960 of the urea, also have a beneficial effect in reducing thetendency of the urea to decompose at elevated temperatures. Examples ofsuch substances are the ammonium salts of strong acids such as ammoniumchloride and ammonium sulphate. The melting point depressants may alsobe decomposition products formed in situ by heating urea above itsmelting point and allowing it to resolidify. If heated for a sufiicienttime (for example from A to 2 hours) at a sufliciently high temperature(for example from to C.)-the resolidified urea has a lower melting pointthan the pure urea and can be used in the process of the presentinvention. The following table shows the reduction in melting pointobtained with different temperatures and'times of heating.

The method of carrying out the present invention may be similar to thatdescribed in US. Serial No. 428,375 and its continuation-in-part SerialNo. 668,043, filed June 26, 1957; thus thetextile materials may beimpregnated with an aqueous solution or dispersion of the urea and themelting point depressant and an aqueous solution or dispersion of thedyestufi? or a single aqueous solution or dispersion ofthe dyestufi, theurea and the melting point depressant, dried, baked to effect thedyeing, washed to remove the urea and dried. The urea and the meltingpoint depressant are preferably applied simultaneously from the samebath in an amount sufficient to give a take up of urea of 40 to 55percent by weight of the dry textile materiaL. The impregnation ispreferably effected at room temperature. on the temperature used; inpractice times varying from 1 /2 to 15 minutes have been found adequate.

The process of the present invention is suitable for dyeing withdyestuffs which are soluble in molten ureafor example direct cottondyestuffs, dispersed acetatedyestufis, soluble acetate dyestulfs, leucoesters of vat dyestuffs, aggregated acid dyestuffs and metal complexdyestuffs. itis particularly suitable for dyeing withv direct cottondyestuffs.

The process of the present invention is suitable for-dyeing thosetextiles which are not deleteriously affected by the baking, for exampletextile materials of cotton, wool, regenerated cellulose, artificialprotein fibres, cellulose esters, synthetic polyamides and syntheticpolyesters and materials made from mixtures of two or moreof thesefibres. If the process is used for dyeing textiles fromthermoplasticrfibres having a comparatively low melting point forexample certain vinyl resin fibres the baking should be carried out atthe lowest temperature and for the shortest time permissible.

The textile materials may be dyed according to the ample, the processmay be applied to woven or knitted fabrics or to threads, yarns orfibres.

the impregnated material may be dried and baked in an oven. 'Theapparatus-normally used for carrying out a The time for the baking stepwill depend creaseeresisttreatment with a urea-formaldehyde resin ontextile materials, can be. used without substantial alters, tron.

In the baking step in the process of the present invention the ureamelts and acts. as a dye transfer medium. The process of the, presentinvention provides a simple and convenient alternative to theestablished practice of dyeing from aqueous dyebaths. The process issimple, quick, easy to. control and eliminates many of thev difiicultiesencountered in dyeing with aqueous dyebaths.

The process is particularly suitable for dyeing blends of two or moredifferent fibres especially where one of the fibres shows a preferentialabsorption for the dyestulf from an aqueous dyebath, for examples blendsof viscose rayon fibres and regenerated protein fibres can be dyed in aneven shade with a direct cotton dyestufi by the process of the presentinvention whereas the blends would be diiferentially dyed from anaqueous dyebath.

The invention is illustrated by the following examples in which theparts are by weight.

Example 1 A fabric woven from 100 percent viscose rayon staple yarn waspadded at 100 percent expression through a solution at room temperatureprepared as follows:

1 part of Durazol Yellow 3115 (LC-II) 40 parts of urea I pa of th ureawere made up to 100 parts with water. The fabric was dried at 80C. andthen baked for 15 minutes at 130 C The dye mpl as heu w shed for m nu esin l water and dried at 80 C.

1 subje t ng the dyed abric to h ash ng t as described in the SecondReport of the Fastness Tests Committee of the Society of Dyers andColourists (Journal of the Society of Dyers and Colourists, 1948, volume64, pages 136-.137, Test No. 1) it was found that the fabric dyed by theprocess of the present invention was of comparable fastness to a fabricdyed from a conventional aqueous dyebath.

Example 2 A fabric woven from 100 percent viscose rayon staple yarn waspadded at 100 percent expression through a solution at room temperatureprepared as follows:

1 part Durazol Rubine BS ('I.C.I.) Color Index 28-160 40 parts of urea 5parts of boric acid were made up to 100 parts with water. The fabric wasdried at 80 C. and then baked for minutes at 130 C. The sample was thenwashed, dried, and the dye fastness assessed according to the testdescribed in Example 1.

Very little dye-was removed by this test.

Example 3 A fabric woven from continuous filament cellulose acetate yarnwas padded at 65 percent expression through the, following solution atroom temperature: 1

3 parts of Duranol Violet 2R 300 (I.C.I.) Color Index 40 par of urea 5 Prts of ly rol p r o D per a (LC-L) Example 4 A solution was prepared asfollows:

1 part of Coomassie Violet 2R (I.C.I.) Color index 45190 40 parts urea 5parts sodium chloride were. made up to 100 parts with water.

A fabric woven from 100 percent continuous filament nylon yarn waspadded through this solution at 60 percent expression and then dried atC. The sample was then split into two equal parts, one only of which wasthen baked for 10 minutes at 130 C., washed in cold water and dried at80 C.

Both samples were subjected to the washing test described in Example 1.The sample which had been baked showed satisfactory dye retention butmuch of the dye on the unbaked sample was removed during the washingtest.

Example 5 A ab c woven f m Pe c n re en a e pr in ap e van; a p e at 0 pr xpr sion hro h a solution prepared as follows:

1 p rt Ca b la B u RS (I-S-D-Q 9 ,1 8 Co r Ind x 52 0 P rt me 5 partsammon um hlo de 2 parts Calsolene Oil were made up to parts with water.The padded fabric was dried at 80 C. and then baked for 10 minutes at C.The dyed fabric was finally washed in cold water and dried at 80 C. Asample subjected to the washing test described in Example 1 showed gooddye retention, very little staining of the undyed fabric being noted.

Example 6 Some urea was heated at C. until the melting point had fallento 124 C. The melt of cooked urea was allowed to resolidify and thenground to a powder.

A solution was prepared as follows:

1 part of Durazol Yellow 3R8 45 parts of cooked urea wer made up o 100pa ts ith ate A fabric woven from 100 percent viscose rayon staple yarnwas p dd d th o h th s l n a 0 pe n expression and dried at 80 C. Thefabric was then a d f 5 m n s a 30 (13., washed a r u e Onsubjectingthedyed fabric to the wash test detailed n Example 1 here was very l ed n te dy nto he ndyed fab ic n e h we c im s:

1. A process for dyeing organic textile materials which comprisesimpregnating the textile material with a solution of a mixture of ureaand at least one another substance which is soluble in molten urea andcapable of lowering the melting point of urea, the amount of saidsubstance in the mixture being sufiicient to lower the melting point ofthe urea by at least 10 C., and with an aqueous solution or dispersionof at least one dyestull which is soluble in molten urea and issubstantive to the textile materiahdrying the textile material at atemperature below the melting point of the mixture of urea and saidsubstance, heating the dried material, in the absence of steam to atemperature between the melting point of the mixture of urea and saidsubstance and 160 C. to melt the mixture whereby the urea in the mixtureserves as a solvent for the dyestutf, from which solution trans for ofthe dyestuif to the material takes place, washing the dyed material toremove the urea and said substance and again drying the material.

24, A process. as. claimed. in claim 1 wherein they textile material isimpregnated with a single solution of urea and the said substance inwhich the dyestufi is dissolved or dispersed.

3. A process as claimed in claim 1 wherein the textile material isimpregnated with an aqueous solution of urea and the said substance.

4. A process as claimed in claim 1 wherein the substance used isthiourea.

5. A process as claimed in claim 1 wherein the substance used is boricacid.

6. A process as claimed in claim 1 wherein the substance used isglycerol.

7. A process as claimed in claim 1 wherein the substance used is sodiumchloride.

8. A process as claimed in claim 1 wherein the substance used isammonium chloride.

9. A process as claimed in claim 1 wherein the textile material isimpregnated with urea in an amount suflicient to give a take-up of ureaof to percent by weight of the dry textilematerial.

10. A process as claimed in claim 9 wherein the amount of depressant isfrom about 8 to about 33 percent of the weight of the urea.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Am. Dyestutr Report, p. 802, November 1950.

1. A PROCESS FOR DYEING ORGANIC TEXTILE MATERIALS WHICH COMPRISES IMPREGNATING THE TEXTILE MATERIAL WITH A SOLUTION OF A MIXTURE OF UREA AND AT LEAST ONE ANOTHER SUBSTANCE WHICH IS SOLUBLE IN MOLTEN UREA AND CAPABLE OF LOWERING THE MELTING POINT OF UREA, THE AMOUNT OF SAID SUBSTANCE IN THE MIXTURE BEING SUFFICIENT TO LOWER THE MELTING POINT OF THE UREA BY AT LEAST 10*C., AND WITH AN AQUEOUS SOLUTION OR DISPERSION OF AT LEAST ONE DYESTUFF WHICH IS SOLUBLE IN MOLTEN UREA AND IS SUBSTANTIVE TO THE TEXTILE MATERIAL, DRYING THE TEXTILE MATERIAL AT A TEMPERATURE BELOW THE MELTING POINT OF THE MIXTURE OF UREA AND SAID, SUBSTANCE, HEATING THE DRIED MATERIAL, IN THE ABSENCE OF STEAM TO A TEMPERATURE BETWEEN THE MELTING POINT OF THE MIXTURE OF UREA AND SAID SUBSTANCE AND 160*C. TO MELT THE MIXTURE WHEREBY THE UREA IN THE MIXTURE SERVES AS A SOLVENT FOR THE DYESTUFF, FROM WHICH SOLUTION TRANSFER OF THE DYESTUFF TO THE MATERIAL TAKES PLACE, WASHING THE DYED MATERIAL TO REMOVE THE UREA AND SAID SUBSTANCE AND AGAIN DRYING THE MATERIAL. 